The man who found a bag of firearms left outside Sir Sadiq Khan's home by armed police officers has said the mayor's security team has "let everyone down".
The incident, which came to light on Friday night, happened earlier this week and five people have been temporarily suspended from frontline duties while an investigation takes place.
Jordan Griffiths called the police after his girlfriend, who is eight months pregnant, found a bag of weapons, including a submachine gun, in a road in south London.
Speaking to Sky News, 30-year-old Griffiths said he initially worried he could end up jailed.
"I put [the bag] on the bed, opened the zip and the first thing I pulled out was the Taser," he said. "I was like, 'oh my god'. Pulled out another one and it was a Glock [pistol].
"Opened up the big bit and the MP5 [submachine gun] was there. I was like, 'what am I going to do now? Am I going to go to prison for this?'. I didn't know what to do."
Mr Griffiths called the police and officers soon arrived to retrieve the bag.
"Anyone could have picked it up, to be honest," he said. "Lucky enough, I came outside and rang the police but anyone could have picked it up.
"There's loads of troublemakers around here. [The mayor's] security have let everyone down, really."
The Metropolitan Police's Directorate of Professional Standards has confirmed it is reviewing what happened.
In a statement, it said: "A member of the public called police after finding a bag containing Met-issued firearms and a Taser on a street in south London.
"Within seven minutes of the call to police, officers arrived at the scene and safely recovered the items.
"At this stage, it is believed the bag was misplaced by on-duty officers a short time before the member of the public located it."
The incident happened at about 9.40pm on Tuesday.
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Griffiths previously told The Sun that police were "really shocked" when they arrived.
"I was told [the guns] had been left there by one of Sadiq Khan's security officers, which made sense as he lives here," he added.
A spokesperson for the mayor said: "This is a very serious incident, which has been referred to the Met's Directorate of Professional Standards.
"The Met must now take all steps to ensure an incident like this never occurs again."
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